The Material Motion Runtime is a tool for describing motion declaratively.

This library does not do much on its own. What it does do, however, is enable the expression of motion as discrete units of data that can be introspected, composed, and sent over a wire.

This library encourages you to describe motion as data, or what we call plans. Plans are committed to a motion runtime, or runtime for short. A runtime coordinates the creation of performers, objects responsible for translating plans into concrete execution.

CocoaPods is a dependency manager for Objective-C and Swift libraries. CocoaPods automates the process of using third-party libraries in your projects. See the Getting Started guide for more information. You can install it with the following command:

gem install cocoapods

Add MaterialMotionRuntime to your Podfile:

pod 'MaterialMotionRuntime'

Then run the following command:

pod install

Import the Material Motion Runtime framework:

@import MaterialMotionRuntime;

You will now have access to all of the APIs.

Check out a local copy of the repo to access the Catalog application by running the following commands:

git clone https://github.com/material-motion/runtime-objc.git
cd runtime-objc
pod install
open MaterialMotionRuntime.xcworkspace

1. Architecture
2. How to define a new plan and performer type
3. How to commit a plan to a runtime
4. How to commit a named plan to a runtime
5. How to handle multiple plan types in Swift
6. How to configure performers with named plans
7. How to use composition to fulfill plans
8. How to indicate continuous performance
9. How to trace internal runtime events
10. How to log runtime events to the console
11. How to observe timeline events

The Material Motion Runtime consists of two groups of APIs: a runtime/transaction object and a constellation of protocols loosely consisting of plan and performing types.

The MotionRuntime object is a coordinating entity whose primary responsibility is to fulfill plans by creating performers. You can create many runtimes throughout the lifetime of your application. A good rule of thumb is to have one runtime per interaction or transition.

The Plan and Performing protocol each define the minimal characteristics required for an object to be considered either a plan or a performer, respectively, by the runtime.

Plans and performers have a symbiotic relationship. A plan is executed by the performer it defines. Performer behavior is configured by the provided plan instances.

Learn more about the Material Motion Runtime by reading the Starmap.

The following steps provide copy-pastable snippets of code.

Questions to ask yourself when creating a new plan type:

• What do I want my plan/performer to accomplish?
• Will my performer need many plans to achieve the desired outcome?
• How can I name my plan such that it clearly communicates either a behavior or a change in state?

As general rules:

1. Plans with an -able suffix alter the behavior of the target, often indefinitely. Examples: Draggable, Pinchable, Tossable.
2. Plans that are verbs describe some change in state, often over a period of time. Examples: FadeIn, Tween, SpringTo.

Code snippets:

In Objective-C:

@interface <#Plan#> : NSObject
@end

@implementation <#Plan#>
@end

In Swift:

class <#Plan#>: NSObject {
}

Performers are responsible for fulfilling plans. Fulfillment is possible in a variety of ways:

• Performing: How to configure performers with plans
• NamedPlanPerforming: How to configure performers with named plans
• ContinuousPerforming: How to indicate continuous performance
• ComposablePerforming: How to use composition to fulfill plans

See the associated links for more details on each performing type.

Note: only one instance of a type of performer per target is ever created. This allows you to register multiple plans to the same target in order to configure a performer. See How to configure performers with plans for more details.

Code snippets:

In Objective-C:

@interface <#Performer#> : NSObject <MDMPerforming>
@end

@implementation <#Performer#> {
  UIView *_target;
}

- (instancetype)initWithTarget:(id)target {
  self = [super init];
  if (self) {
    assert([target isKindOfClass:[UIView class]]);
    _target = target;
  }
  return self;
}

- (void)addPlan:(id<MDMPlan>)plan {
  <#Plan#>* <#casted plan instance#> = plan;

  // Do something with the plan.
}

@end

In Swift:

class <#Performer#>: NSObject, Performing {
  let target: UIView
  required init(target: Any) {
    self.target = target as! UIView
    super.init()
  }

  func addPlan(_ plan: Plan) {
    let <#casted plan instance#> = plan as! <#Plan#>

    // Do something with the plan.
  }
}

Conforming to Plan requires:

1. that you define the type of performer your plan requires, and
2. that your plan be copyable.

Code snippets:

In Objective-C:

@interface <#Plan#> : NSObject <MDMPlan>
@end

@implementation <#Plan#>

- (Class)performerClass {
  return [<#Plan#> class];
}

- (id)copyWithZone:(NSZone *)zone {
  return [[[self class] allocWithZone:zone] init];
}

@end

In Swift:

class <#Plan#>: NSObject, Plan {
  func performerClass() -> AnyClass {
    return <#Performer#>.self
  }
  func copy(with zone: NSZone? = nil) -> Any {
    return <#Plan#>()
  }
}

Code snippets:

In Objective-C:

@interface MyClass ()
@property(nonatomic, strong) MDMMotionRuntime* runtime;
@end

- (instancetype)init... {
  ...
  self.runtime = [MDMMotionRuntime new];
  ...
}

In Swift:

class MyClass {
  let runtime = MotionRuntime()
}

Code snippets:

In Objective-C:

[runtime addPlan:<#Plan instance#> to:<#View instance#>];

In Swift:

runtime.addPlan(<#Plan instance#>, to:<#View instance#>)

Code snippets:

In Objective-C:

@interface MyClass ()
@property(nonatomic, strong) MDMMotionRuntime* runtime;
@end

- (instancetype)init... {
  ...
  self.runtime = [MDMMotionRuntime new];
  ...
}

In Swift:

class MyClass {
  let runtime = MotionRuntime()
}

Code snippets:

In Objective-C:

[runtime addPlan:<#Plan instance#> named:<#name#> to:<#View instance#>];

In Swift:

runtime.addPlan(<#Plan instance#>, named:<#name#>, to:<#View instance#>)

Make use of Swift's typed switch/casing to handle multiple plan types.

func addPlan(_ plan: Plan) {
  switch plan {
  case let <#plan instance 1#> as <#Plan type 1#>:
    ()

  case let <#plan instance 2#> as <#Plan type 2#>:
    ()

  case is <#Plan type 3#>:
    ()

  default:
    assert(false)
  }
}

Code snippets:

In Objective-C:

@interface <#Performer#> (NamedPlanPerforming) <MDMNamedPlanPerforming>
@end

@implementation <#Performer#> (NamedPlanPerforming)

- (void)addPlan:(id<MDMNamedPlan>)plan named:(NSString *)name {
  <#Plan#>* <#casted plan instance#> = plan;

  // Do something with the plan.
}

- (void)removePlanNamed:(NSString *)name {
  // Remove any configuration associated with the given name.
}

@end

In Swift:

extension <#Performer#>: NamedPlanPerforming {
  func addPlan(_ plan: NamedPlan, named name: String) {
    let <#casted plan instance#> = plan as! <#Plan#>

    // Do something with the plan.
  }

  func removePlan(named name: String) {
    // Remove any configuration associated with the given name.
  }
}

A composition performer is able to emit new plans using a plan emitter. This feature enables the reuse of plans and the creation of higher-order abstractions.

Code snippets:

In Objective-C:

@interface <#Performer#> ()
@property(nonatomic, strong) id<MDMPlanEmitting> planEmitter;
@end

@interface <#Performer#> (Composition) <MDMComposablePerforming>
@end

@implementation <#Performer#> (Composition)

- (void)setPlanEmitter:(id<MDMPlanEmitting>)planEmitter {
  self.planEmitter = planEmitter;
}

@end

In Swift:

// Store the emitter in your class' definition.
class <#Performer#>: ... {
  ...
  var emitter: PlanEmitting!
  ...
}

extension <#Performer#>: ComposablePerforming {
  var emitter: PlanEmitting!
  func setPlanEmitter(_ planEmitter: PlanEmitting) {
    emitter = planEmitter
  }
}

Performers are only able to emit plans for their associated target.

Code snippets:

In Objective-C:

[self.planEmitter emitPlan:<#(nonnull id<MDMPlan>)#>];

In Swift:

emitter.emitPlan<#T##Plan#>)

Performers will often perform their actions over a period of time or while an interaction is active. These types of performers are called continuous performers.

A continuous performer is able to affect the active state of the runtime by generating activity tokens. The runtime is considered active so long as an activity token is active. Continuous performers are expected to activate and deactivate tokens when ongoing work starts and finishes, respectively.

For example, a performer that registers a platform animation might activate a token when the animation starts. When the animation completes the token would be deactivated.

Code snippets:

In Objective-C:

@interface <#Performer#> ()
@property(nonatomic, strong) id<MDMPlanTokenizing> tokenizer;
@end

@interface <#Performer#> (Composition) <MDMComposablePerforming>
@end

@implementation <#Performer#> (Composition)

- (void)givePlanTokenizer:(id<MDMPlanTokenizing>)tokenizer {
  self.tokenizer = tokenizer;
}

@end

In Swift:

// Store the emitter in your class' definition.
class <#Performer#>: ... {
  ...
  var tokenizer: PlanTokenizing!
  ...
}

extension <#Performer#>: ContinuousPerforming {
  func givePlanTokenizer(_ tokenizer: PlanTokenizing) {
    self.tokenizer = tokenizer
  }
}

If your work completes in a callback then you will likely need to store the token in order to be able to reference it at a later point.

Code snippets:

In Objective-C:

id<MDMTokenized> token = [self.tokenizer tokenForPlan:<#plan#>];
tokenMap[animation] = token;

In Swift:

let token = tokenizer.generate(for: <#plan#>)!
tokenMap[animation] = token

Code snippets:

In Objective-C:

id<MDMIsActiveTokenable> token = tokenMap[animation];
token.active = true;

In Swift:

tokenMap[animation].isActive = true

Code snippets:

In Objective-C:

id<MDMTokenized> token = tokenMap[animation];
token.active = false;

In Swift:

tokenMap[animation].isActive = false

Tracing allows you to observe internal events occurring within a runtime. This information may be used for the following purposes:

• Debug logging.
• Inspection tooling.

Use for other purposes is unsupported.

Code snippets:

In Objective-C:

@interface <#Custom tracer#> : NSObject <MDMTracing>
@end

@implementation <#Custom tracer#>
@end

In Swift:

class <#Custom tracer#>: NSObject, Tracing {
}

The documentation for the Tracing protocol enumerates the available methods.

Code snippets:

In Objective-C:

@implementation <#Custom tracer#>

- (void)didAddPlan:(id<MDMPlan>)plan to:(id)target {

}

@end

In Swift:

class <#Custom tracer#>: NSObject, Tracing {
  func didAddPlan(_ plan: Plan, to target: Any) {

  }
}

Code snippets:

In Objective-C:

[runtime addTracer:[MDMConsoleLoggingTracer new]];

In Swift:

runtime.addTracer(ConsoleLoggingTracer())

Code snippets:

In Objective-C:

@interface <#SomeClass#> () <MDMTimelineObserving>
@end

@implementation <#SomeClass#>

- (void)timeline:(MDMTimeline *)timeline didAttachScrubber:(MDMTimelineScrubber *)scrubber {

}

- (void)timeline:(MDMTimeline *)timeline didDetachScrubber:(MDMTimelineScrubber *)scrubber {

}

- (void)timeline:(MDMTimeline *)timeline scrubberDidScrub:(NSTimeInterval)timeOffset {

}

@end

In Swift:

extension <#SomeClass#>: TimelineObserving {
  func timeline(_ timeline: Timeline, didAttach scrubber: TimelineScrubber) {
  }

  func timeline(_ timeline: Timeline, didDetach scrubber: TimelineScrubber) {
  }

  func timeline(_ timeline: Timeline, scrubberDidScrub timeOffset: TimeInterval) {
  }
}

Code snippets:

In Objective-C:

[timeline addTimelineObserver:<#(nonnull id<MDMTimelineObserving>)#>];

In Swift:

timeline.addObserver(<#T##observer: TimelineObserving##TimelineObserving#>)

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